The plastic granulate, produced by a processing plant regularly requires additional treatment which consists essentially of cooling the plastic granulate in a stream of water, separating it from the transport water and freeing it from the water adhering to its surface.
The known additional treatment therefore employs a number of devices which are interconnected by pipelines which take up a great deal of space after a cutting device for the plastic granulate.
One essential component of these devices is a dewatering rotor in which the mixture of plastic granulate and water is mechanically separated and fed to storage or tank means.
The large amount of space required for this dewatering device which is formed of several interconnected devices and the large amount of water stored and circulating therein are particularly disadvantageous.
This has a detrimental effect, particularly when the product is changed, i.e., the entire plant is converted for handling another type of product. Since no residual granulate of the preceding product must remain in the granulate/water transport region, the system must be entirely cleaned before changing the product.
Frequently, complete replacement of the water stored in the additional treatment system is necessary, which is also very time-consuming and costly.
Another disadvantage of the currently utilized equipment is the high amount of energy required for the mechanical separation of the water and the noise which is developed.
DE-OS No. 3 120 792 discloses a granulate drier of the aboveindicated type in which the mixture of plastic granulate and water is fed to a dewatering rotor which is vertically mounted in a housing. The feed takes place at one end through the bottom of a screening member which surrounds the dewatering rotor, while the removed water is discharged through a connection in the bottom of the housing. In this case, the entire mixture of granulate and water is fully accelerated and thrown against the screen for a partial removal of the water in a first rotor stage for which a considerable expenditure of energy is required. Plastic granulate which has a specific gravity of more than 1 can have the water removed from it only with difficulty in the known apparatus since the feed easily becomes clogged.
In order to use the known granulate drier additional devices are required which, including the required pipelines, result in a considerable expenditure of space.